Radio apparatus



Aug. 2 8, 192s. 1,682,103

RADIO APPARATUS Filed Oct. 8, 1920 l MyW ATTORNEY Patented Aug. 28,1928.

UNITED STATES PATENT OFFICE.

DONALD LITTLE, QF DGEWOOD, PENNSYLVANIA, ASSIGNOR TO RADIO CORPORA- TIONOF AMERICA, A (LORPORATION` OF NEW YORK.

RADIO APPARATUS.

Application led October 8, 1920. Serial No. 415,523.

My invention relates to radiol apparatus of the type in which anoscillation circuit is adapted to be tuned to various wave-lengthswithin a given range, and its object is to provide a system whereby thenecessary adjustments or manipulations for changing the wave-length maybe reduced to a minimum.

A more specific object of my invention is to provide aradio-transmitting circuit of uniform output over a large range ofwavelengths. A further object is the attainment of the aforesaid objectswith minimum loading and minimum adjustments of loading of the variouscoupled circuits.

These and other objects are obtained by means of the apparatushereinafter described and claimed, and illustrated in its preferredform. in the accompanying drawing, in which the figure is a diagrammaticView of a transmitting set embodying my invention.

The apparatus is shown as consisting of an oscillation circuit 1,comprising an antenna'2 and a variable inductance 3, whereby saidcircuit may be tuned to various wave-lengths within a given range. Ifdesired, a rough adjustment only may be made with the variableinductance 3, the final tuning being accomplished by means of a variableshunt condenser 4. The inductance 3 is shown connected to ground at 5.The inductance 3 is 1n inductive relationship with a coil 6, theterminals of which are connected respectively to the filament 7 and theplate 8` of a three-electrode vacuum tube 9. The grid 10 of said tube isconnected to one terminal of a second inductively related coil H,thenther terminal of which is connected to the filament 7 A gridcondenser 12 is shown bridged by a resistance At any convenient pointinl the plate circuit of the vacuum tube I place any suitable source ofenergy, indicated by the signs plus and minus, which is bridged by acondenser 14, although my invention is not limited to the use of adirect-current source.

The usual preventive impedances 15 are shown in the conductors 16 and 17leading to said source.

Coil 6 is bridged by a suitable capacity 18, forming a tuned circuit.When no current is flowing in the antenna circuit, the circuitcomprising the coil 6 and capacity 18 is arranged to have a wave-lengthwhich is shorter than the shortest wave-length to which said antennacircuit may be adjusted. When current is flowing through the antennacircuit, the latter, as Well as the local plate circuit, comprising thecoil 6 and capaclty 18, Oscillate at the wave-length determined by theconstants of the antenna circuit.-

f If desired, the `common terminal of coils 6 and 11, which is joined tothe filament 7, may be connected to ground by means of the conductor 19.

I have discovered that the plate circuit functions as an untuned circuitin that it is not tuned to the wave-length of the antenna circuit, butdoes transmlt impressed waves of the wave-length to which the antennacircuit is tuned, whereas the plate circuit is tuned to the extent thatany variation of the plate condenser 18 changes the power output of theantenna circuit. In practice, upon setting the plate condenserl 18 tothe desired adjusted position, its adjustment is not disturbed.

In the practice of my invention, the output over a wide variation ofantenna capacity and resistance is maintained substantially uniform andthe load on the Oscillating tube or tubes remains practically constant.The

desired particular wave-length sought to be emitted from the antenna isreadily regulated by solely varying the variable inductance 3 andvariable condenser.

l Since the parallel resonant circuit 6, 18 is serially included in theplate circuit, and Since said parallel resonant circuit is tuned to awave-length slightly less than the lowest wave-length to which theantenna circuit is to be tuned, the circulating current in the coil 6will decrease as the frequency departs further and further from thecondition of exact resonance. Hence, the effective ampereturns ofthecoupling coil 6 are decreased as the antenna wave-length isincreased, there by counteracting the effect of the increasedampere-turns in the tuning coil 3 and also maintaining a substantiallyconstant output over a considerable range of wave-lengths, with a singleadjustment of the tuning coil 3. Whereas I have described my inventionby reference to specific forms thereof, it will be understood that l donot regard my invention as being limited to the exact details ofconstruction shown, as many changes and modifications may be madewithout departing from the 'spirit of the invention as deinedby theappended claims.

I. claim as my invention :w-

1. In a radio transmission system, an oscillation circuit adapted to betuned to various wave lengths within a given range, in combination withan oscillation generator, including said circuit and comprising anamplifier having an input circuit and an output circuit, said circuitshaving a feed-back arrangement whereby some of the power from the outputcircuit is impressed upon the input circuit,

and. said amplifier delivering to said output circuit a relatively largepower upon the reception of a relatively small power from said inputcircuit, and means including a local source for supplying said amplifierwith energy, one of the circuits of said generator havingr includedtherein a circuit with a natural wave length outside the range of wavelengths of said oscillation circuit, said included circuit being coupledto said oscillation circuit and the constants of the coupled circuitsbeing such that theinterchange of power between them may besubstantially the same regardless of the adjustment of said oscillationcircuit.

2. In a radio transmission system, an oscillation circuit adapted to betuned to various wave lengths within a given range, in combination withan oscillation generator, including said circuit and comprising anamplifier having an input circuit and an output circuit, said circuitshaving a feed-back arrangement, whereby some of the power from theoutput circuit is impressed upon the input circuit, and said amplifierdelivering to said output circuit, a relatively large power upon thereception of a relatively small power from said input circuit, and meansincluding a local source of energy for supplying said amplifier, one ofthe circuits of said generator having included therein a circuit with anatural wave length shorter than the shortest wave length to which saidoscillation circuit may be adjusted, whereby the interchange of powerbetween said circuits may be substantially the same regardless of theadjustment of said oscillation circuit.

3. In a radio transmission system, an oscillation circuit including avariable inductance and a capacity capable of but slight variation,whereby said circuit may be tuned to various wavelengths within a givenrange, in combination with an oscillation generator, including saidoscillation circuit and comprising an amplifier havin an input circuitand an out put circuit, sai circuits having a feed-back arrangement,whereby some of the power `from the output circuit is impressed upon theinput circuit, and said amplifier delivering to said output circuit arelatively large power upon the reception of a relatively small powerfrom said input circuit, and means including a local source forsupplying said amplifier power between said circuits may besubstantially the same regardless of the adjustment of said oscillationcircuit.

4. In a radio-transmission system, the combination with an oscillationcircuit including a variable inductance and a capacity capable of butslight variation, whereby said circuit may be tuned to variouswave-lengths within a given range, of a threeelectrode vacuum tubehaving a late circuit and a grid circuit, both of said ast mentionedcircuits being inductively coupled with said variable inductance, one ofsaid last-mentioned circuits including a parallel resonant circuit, theinductive clement of which forms one member of the vcoupling ofthis tubecircuit with said variable inductance, said parallel resonant circuithaving a natural wave-length which is shorter than the shortestwave-length to which said oscillation circuit may be adjusted, and meanswhereby a source of energy may be connected to said vacuum tube, theconstants of said circuits being such that the power delivered to saidoscillation circuit is substantially constant for all wave-lengths.

5. In a radio-transmission system, the combination with `a secondarycircuit adaptedtobe tuned to various wave-lengths within a given range,of an oscillation generator including said secondary circuit and havinga power circuit and a controlling circuit for controlling the current insaid power circuit, and means for supplying energy thereto saidoscillation-generator circuits including a primary circuit coupled tosaid secondary circuit, and said primary circuit having a naturalwavelength not included in the range of variation of said Secondarycircuit.

6. In a radio-transmission system, the combination with an oscillationcircuit adapted to be tuned to various wave-lengths within a givenrange, of an oscillation generator including said oscillation circuitand compris ing an amplifier having a controlling circuit and an outputcircuit coupled to said controlling circuit and a source of energyconnected to said output circuit, said output circuit serially includinga parallel resonant circuit inductively coupled to' said oscillationcircuit and having a constant natural wave-length which is shorter thanthe shortest wave-length of said oscillation circuit.

7. In radio apparatus, the combination with an oscillation circuitincluding a substantially constant capacity and a variable inductance,whereby said circuit may be tuned to various wave-lengths within a givenrange, of a second circuit inductively coupled with said variableinductance, said second circuit having anatural wave-length which isshorter than the shortest wavelength to which said oscillation circuitmay be adjusted, the constants being such that the interchange of powerbetween said circuits is substantially the same regardless of theadjustment of said oscillation circuit, an output circuit including saidsecond circuit and including also a source of energy and a variableimpedance device, a controlling circuit for varying said variableimpedance, and means for coupling said controlling circuit to receivepower from said output circuit. i

8. In radio apparatus, the combination with an oscillation circuitincluding a substantially constant capacity and a variable inductance,whereby said circuit may be tuned to various wave-lengths within a givenrange, of a parallel resonant circuit inductively coupled to saidvariable inductance, said parallel resonant circuit having forcedoscillations and having a constant natural wave-length which is shorterthan the shortest wave-length of said oscillation circuit, a variableimpedance device, electroeresponsive controlling means therefor, asource of energy, an output circuit including said variable impedancedevice, said source of energy and said parallel resonant circuit, andmeans for coupling said controlling means to be responsive to theelectrical conditions in saidoutput circuit.

9. In radio apparatus, the combination with an oscillation circuitincluding a substantially constant capacity and a variable inductance,whereby said circuit may be tuned to various wave-lengths within a givenrange, of a parallel resonant circuit inductively coupled to saidvariable inductance, said parallel resonant circuit having forcedoscillations 'and having a constant natural wave-length which is shorterthan the shortest Wave-length of said oscillation circuit, an electrontube having a space-current path, controlling means therefor, a sourceof energy, an out put circuit including said space-current path, saidsource of energy and said parallel res` onant circuit, and means f orcoupling said controlling means to receive power from said outputcircuit.

10. In a radio system, a tunable oscillation circuit, a circuit coupledthereto, said coupled circuit having'a tuning device in addition to thecoupling, the natural period of said coupled circuit being outside therange of frequencies to which said oscillation circuit is tunable.

11. An electron-discharge oscillator comprising a discharge devicehaving electrodes,

a tuned frequency-determining circuit associated therewith, a circuitincluding the capacity between two ormore of said electrodes capable ofacting as a frequency-determining circuit for waves of a parasiticfrequency other than the ldesired frequency, and means associated withsaid device for establishing said parasitic frequency at such' a valueother than the desired frequency as will prevent the reduction of poweroutput at the desired frequency.

l2. An electron discharge oscillator comprising a discharge devicehaving electrodes, one of said electrodes being a cathode having aground connection, a tuned frequency-de termining circuit connected toground and insulated from said device except for said ground connection,a circuit separate from said tuned frequency-determining circuit andincluding the capacity inherent in said device and its leads, saidcircuit tending to act as a frequency determining circuit for parasiticoscillations, and means attached to said circuit for preventing thetendency of said device to oscillate at said parasitic frequency fromreducing the power output at the de sired frequency.

13. In a power oscillator, a space discharge device having an anode, acathode, and a control element for controlling the discharge between theanode and the cathode, a tuned frequency determining circuit coupled tothe circuits of said device an inductance coil in the anode-cathodecircuit coupled to said tuned circuit,and a condenser shunted aroundsaid coil for increasing the power factor of the anode-cathode'circuitat the frequency of generation, said coil and condenser shuntedthere-around being of such values as to form a resonant combination onlyat a frequency considerably different from the frequency of generation.

14. In a radio transmission system, the combination of an oscillationcircuit, means for varying the tuning of said oscillation circuit over arange of wave lengths, a threeelectrode vacuum tube having grid andplate circuits inductively coupled to said oscillation circuit, a sourceof energy connected to said vacuum tube, and included in one of saidtube circuits a parallel resonant circuit having a natural wave lengthdifferent from that of said oscillation circuit, the constants of saidcircuits being such that the power delivered to said oscillation circuitis substantially constant for all wave lengths within said range.

In testimony whereof I aihx my signature.

DONALD G. LITTLE.

